1. Field of the Invention
This invention relates to the mechanical stabilization of particulate media, and more particularly to the use of a piston in maintaining a bed in a compacted state throughout its operation to enhance bed performance.
2. Description of the Related Art
Column performance of ion exchange and other particulate media during column elution can be improved if the material is taken off the column in a direction which is the reverse of that which was used for loading. This results in a more concentrated eluant. This process is impeded by the propensity of the bed material to channel under reverse flow when compacted by gravitation force only. What is needed is a method of compressing the bed to prevent channeling while allowing for expansion and contraction of the bed.
U.S. Pat. No. 5,169,522, issued to Y. Shalon et al. discloses a method for compressing beds of particles for use in chromatographic columns which consist of a metallic piston in a metallic cylinder which provides for pressurization of the piston in order to compress the bed. The method requires the cylinder to be flanged on both ends with the piston inside. It requires penetration of the flange to convey the fluid through the flexible tubing to the piston and also penetration of the flange to airload or pressurize the piston with the gas.
U.S. Pat. No. 4,597,866, issued to F. Couillard, discloses a chromatographic column assembly comprising a tubular column with both ends sealed. An internal piston is used to compress a particulate bed. The compressive force results from gas loading of the piston. It requires a pressurizing system and the column to be sealed at both ends.